#include <iostream.h>
#include <fstream.h>
fstream f("fact.in",ios::in);
fstream g("fact.out",ios::out);
int main()
{long long p,n,d;
unsigned int k,i;
f>>p;
f.close();
n=0;
i=0;
if(p==0){ g<<"1";i=1;}
if(p<0) { g<<"-1";i=1;}

if(p>0) while(p>0){n=n+5;
		   p--;
		   d=n/5;
		   k=1;
		   while(k==1)
			 if(d%5==0) {p--;d=d/5;}
			     else k=0;
		  }

 if(i==0) g<<n;
g.close();
return 0;
}